Polina Dimitrova

Dr. Polina Dimitrova

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Research Focus & Metrics

Academic Career Length

5Years (2022-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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24 December 2022 in Diagnostics
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Journal Article
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angel yordanovangel yordanov
angel yordanov
VSVelizar Shivarov
Velizar Shivarov
Stoyan KostovStoyan Kostov
Stoyan Kostov
YIYonka Ivanova
Yonka Ivanova
PDPolina Dimitrova
Polina Dimitrova
MVMariela Vasileva-Slaveva
Mariela Vasileva-Slaveva
Introduction: Cancer of the uterine cervix (CUC) is still one of the most frequent oncological diagnoses in women. The specific interactions between the tumor cells of CUC and the cells and tissues in the tumor microenvironment can affect cancer cells’ invasive and metastatic potential and can modulate tumor’s progression and death. CD47 is a trans-membranous immunoglobulin, expressed in many cells. It protects the cells from being destroyed by the circulating macrophages. Aim: We aimed to evaluate the prognostic role of CD47 expressed in the tumor tissues of patients with CUC for tumor progression and to find the most sensitive immunohistochemical score for defining the cut-off significantly associated with tumor biology and progression. Materials and methods: Paraffin-embedded tumor tissues from 86 patients with CUC were included in the study. Clinico-morphological data for patients, such as age and stage at diagnosis according to FIGO and TNM classification, were obtained from the hospital electronic medical records. Immunohistochemical staining was performed with rabbit recombinant monoclonal CD47 antibody (Clone SP279). The final result was interpreted based on three reporting models in immunohistochemistry: H-score, Allred score and combined score. Results: The expression of CD47 was higher in tumors limited in the cervix compared with those invading other structures, and it did not depend on the nodal status. The results of immunohistochemical staining were similar regardless of which immunohistochemical method was used. The most significant correlation with TNM stage was observed with the H-score (p = 0.00018). The association with the Allred and combined score was less significant, with p values of 0.0013 and 0.0002, respectively. Conclusion: The expression of CD47 in the cancer cells is prognostic for tumor invasion in the surrounding structures, independent of lymph node engagement. The H-score is the most sensitive immunohistochemical score to describe tumor stage. To the best of our knowledge, this is the first study evaluating the significance of CD47 expression in CUC.

7 April 2023 in Medicina
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Journal Article
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PDPolina Dimitrova
Polina Dimitrova
MVMariela Vasileva-Slaveva
Mariela Vasileva-Slaveva
VSVelizar Shivarov
Velizar Shivarov
Ihsan HasanIhsan Hasan
Ihsan Hasan
angel yordanovangel yordanov
angel yordanov
Background and Objectives: The tumor microenvironment (TME) plays a major role in neoplastic development. Various types of cells can be found in the TME. These cells can be classified into two groups, immunosuppressive and immunostimulatory types, depending on the function they perform in the antitumor immune response (IR). By interacting both with each other and with tumor cells, different immune mechanisms are activated or inhibited, which can suppress or promote the development and progression of cervical cancer (CC). Our aim was to investigate some of the main components of the cellular immune response in TME—tumor-infiltrating cytotoxic T cells (Tc, CD8+) and tumor-associated macrophages (TAMs, CD68+)—in patients with CC. Materials and Methods: We analyzed 72 paraffin-embedded tumor tissues of patients diagnosed and treated at Medical University Pleven, Bulgaria. Patients were classified according to the 2018 FIGO (International Federation of Gynaecology and Obstetrics) classification. From each patient, we selected one histological slide with hematoxylin eosin staining. In a microscopic evaluation, CD8+ T lymphocytes and CD68+-positive macrophages were counted in the tumor and stroma of five randomly selected fields at ×40 magnification (HPF). We analyzed the relationship between intratumoral and stromal CD8 and CD68 expression and FIGO stage and N status. Results: There was no significant association between the expression levels of intratumoral and stromal CD68+ cells in the different FIGO stages and according to the lymph nodes’ involvement. For CD8+ cells, the association of stromal infiltration was also not found, but T intratumor infiltration was associated with a higher FIGO stage, despite the fact that the results did not reach significance (p = 0.063, Fisher test). Intratumoral CD8+ cells were significantly associated with positive N status, (p = 0.035). Discussion: The separation of tumor-infiltrating cytotoxic T cells and tumor-associated macrophages into intratumoral and stromal is inconsequential. In our study, the level of infiltration of CD68+ cells in tumors and stromata was not significantly associated with tumor progression or lymph node involvement. The results were different for CD8+ cells, in which levels of infiltration were associated with lymph nodes’ statuses. Conclusions: The separate evaluation of CD68+ immune cells in the TME as intratumoral and stromal is not beneficial for defining prognoses, since the presence of these cells is not associated with the patient’s stage. In our study, the presence of CD8+ cells was significantly associated with lymph node metastases. The prognostic value of the obtained results can be enriched with an additional study of the lymphocyte phenotype, including B and other subtypes of T lymphocytes, NK cells, as well as molecules involved in the immune response, such as HLA subtypes.

9 September 2025 in Biomedicines
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Journal Article
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angel yordanovangel yordanov
angel yordanov
PDPolina Dimitrova
Polina Dimitrova
MVMariela Vasileva-Slaveva
Mariela Vasileva-Slaveva
KKKonstantina Karakadieva
Konstantina Karakadieva
Stoyan KostovStoyan Kostov
Stoyan Kostov
VSVelizar Shivarov
Velizar Shivarov
Background and Objectives: Cervical cancer (CC), primarily caused by human papillomavirus (HPV) infection, is the most common gynecological cancer and a leading cause of cancer-related death in women. The immune microenvironment, particularly CD4+ T-helper cells and FOXP3 (forkhead box P3)+ regulatory T cells (Tregs), plays a crucial role in tumor progression. However, the exact relationship between immune cell infiltration and clinical outcomes in CC is not fully understood. This study aimed to examine the association between CD4+ T-helper cells, FOXP3+ Tregs, and clinical/pathological parameters in CC patients. Methods: We conducted a retrospective analysis of 150 patients with T1-stage cervical cancers diagnosed between 2015 and 2021. Tumor samples were evaluated using immunohistochemistry (IHC) to assess CD4+ and FOXP3+ TILs in intratumoral and stromal regions. Additionally, deconvoluted transcriptomic data from the TCGA cohort were used to assess immune infiltration within the tumor immune microenvironment (TIME). Results: High infiltration of CD4+ T-helper cells was significantly associated with better overall survival (OS) in node-negative CC patients (p = 0.0006). However, no significant prognostic value was found for Tregs. CD4+ cells were more prevalent in patients with well-differentiated tumors (G1 and G2) and lower levels of CD4+ infiltration were found in squamous cell carcinoma (SCC) compared to other histological subtypes. Multivariate regression analysis showed that only tumor size (T1b3) and undifferentiated tumor morphology (G3) were significantly associated with poorer OS. In contrast, infiltration of CD4+ or FOXP3+ cells did not significantly correlate with OS after adjusting for clinical factors. Competing risk analysis for death from cancer showed no significant associations with immune cell infiltration levels. Conclusions: This study underscores the complex relationship between immune cell infiltration and clinical outcomes in CC. While CD4+ T-helper cell infiltration is associated with improved prognosis in node-negative cases, further research is necessary to clarify the role of Tregs and other immune components in the tumor microenvironment. These findings suggest potential avenues for therapeutic strategies, including immune checkpoint inhibitors, in CC.

Verified
Journal Article
Open access
PDF file
angel yordanovangel yordanov
angel yordanov
PDPolina Dimitrova
Polina Dimitrova
MVMariela Vasileva-Slaveva
Mariela Vasileva-Slaveva
Ihsan HasanIhsan Hasan
Ihsan Hasan
Stoyan KostovStoyan Kostov
Stoyan Kostov
VSVelizar Shivarov
Velizar Shivarov
Despite improvements in vaccination, screening, and treatment, cervical cancer (CC) remains a major healthcare problem on a global scale. The tumor microenvironment (TME) plays an important and controversial role in cancer development, and the mechanism of the tumor’s escape from immunological surveillance is still not clearly defined. We aim to investigate the expression of CD68 and CD47 in patients with different histological variants of CC, tumor characteristics, and burden. This is a retrospective cohort study performed on paraffin-embedded tumor tissues from 191 patients diagnosed with CC between 2014 and 2021 at the Medical University Pleven, Bulgaria. Slides for immunohistochemical (IHC) evaluation were obtained, and the expression of CD68 was scored in intratumoral (IT) and stromal (ST) macrophages (CD68+cells) using a three-point scoring scale. The CD47 expression was reported as an H-score. All statistical analyses were performed using R v. 4.3.1 for Windows. Infiltration by CD68-IT cells in the tumor depended on histological type and the expression of CD47. Higher levels of the CD47 H-score were significantly more frequent among patients in the early stage. Higher levels of infiltration by CD68-ST cells were associated with worse prognosis, and the infiltration of CD68-IT cells was associated with reduced risk of death from neoplastic disease. TME is a complex ecosystem that has a major role in the growth and development of tumors. Macrophages are a major component of innate immunity and, when associated with a tumor process, are defined as TAM. Tumor cells try to escape immunological surveillance in three ways, and one of them is reducing immunogenicity by the overexpression of negative coreceptors by T-lymphocytes and their ligands on the surface of tumor cells. One such mechanism is the expression of CD47 in tumor cells, which sends a “don’t eat me” signal to the macrophages and, thus, prevents phagocytosis. To our knowledge, this is the first study that has tried to establish the relationship between the CD47 and CD68 expression levels and some clinicopathologic features in CC. We found that the only clinicopathological feature implicating the level of CD68 infiltration was the histological variant of the tumor, and only for CD68-IT–high levels were these observed in SCC. High levels of CD47 expression were seen more frequently in pT1B than pT2A and pT2B in the FIGO I stage than in the FIGO II and III stages. Infiltration by large numbers of CD68-IT cells was much more common among patients with a high expression of CD47 in tumor cells. A high level of infiltration by CD68-ST cells was associated with a worse prognosis, and a high level of infiltration by CD68-ST cells was associated with a lower risk of death from cancer.

21 December 2025 in Diagnostics
Verified
Journal Article
Open access
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ETEva Tsoneva
Eva Tsoneva
PDPolina Dimitrova
Polina Dimitrova
MMMetodi V Metodiev
Metodi V Metodiev
VSVelizar Shivarov
Velizar Shivarov
MVMariela Vasileva-Slaveva
Mariela Vasileva-Slaveva
RWRafał Watrowski
Rafał Watrowski
Background: Cervical cancer (CC) is the fourth most common malignancy in women around the world, with more than 600,000 new cases registered in 2022 and around 350,000 deaths. It is a growing social problem, especially in developing countries. Almost all cases of cervical cancer are caused by persistent infection with oncogenic high-risk human papillomavirus (HPV). This malignancy usually exhibits a gradual development through well-defined precursor stages, known as cervical intraepithelial neoplasia (CIN) grades 1, 2, and 3, before evolving into invasive carcinoma. In diagnostic practice, several biomarkers have been implemented to improve the detection of high-risk cervical lesions. p16 and Ki-67 greatly aid in identifying HPV-driven dysplasia, but they cannot always reliably distinguish progressive lesions from regressive or transient HPV infections. These limitations highlight the need for novel biomarkers with better predictive accuracy to complement current screening and diagnostic algorithms. ROMO1 has become a possible marker of a high-ROS, high-risk tumor phenotype in a number of cancers. Although oxidative stress, HPV, and cervical carcinogenesis have been linked, nothing is known about ROMO1’s involvement in cervical neoplasia. There is currently a lack of thorough information regarding the expression of ROMO1 in normal vs. precancerous lesions and in cervical cancer, as well as on whether or not its expression is correlated with the severity of the disease. In order to define ROMO1 expression throughout the course of cervical squamous neoplastic development, the current study was created. Methods: We performed immunohistochemical analysis of ROMO1 expression on cervical tissue samples from three groups: healthy cervix (n = 30), cervical intraepithelial neoplasia (CIN) (n = 41), and invasive cervical carcinoma (n = 205). ROMO1 expression in invasive carcinoma was evaluated using an H-score scale. Results: ROMO1 expression was basal in all normal cervix samples (0/30 cases). In contrast, CIN lesions showed 100% ROMO1 expression in the suprabasal layers of abnormal cells in all CIN cases. In invasive cervical carcinomas, ROMO1 expression was heterogeneous. In our cancer cohort (n = 205), ROMO1 H-score showed no significant association with the following: FIGO stage I vs. II vs. III (p = 0.25); histologic grade G1 vs. G2 vs. G3 (p = 0.46); lymphovascular invasion (no vs. yes; p = 0.80); nodal status N0 vs. N1 (p = 0.67); patient age (≤50 y vs. >50 y; p = 0.38). However, ROMO1 expression did vary by histologic subtype (AC vs. ASC vs. SCC; p = 0.02), with SCC enriched for strong staining compared to AC/ASC. With regard to tumor stage (pT stage), pT2a tumors exhibited significantly lower ROMO1 (pT1b1–pT2b; p = 0.035) than pT1b1 (p = 0.04). No other clinicopathologic variable remained significant. Notably, ROMO1 expression was highest in stage I tumors and declined in more advanced stages of cervical carcinoma. Conclusions: These results show a clear pattern of ROMO1 expression across the cervical neoplasia spectrum: it is attenuated in invasive tumors (with a peak in early-stage illness), significantly raised in pre-cancerous CIN lesions, and negligible in normal epithelium. The idea that oxidative stress may be the primary cause of early malignant transformation in the cervix is supported by the noticeable overexpression of ROMO1 in early lesions. For the detection of early-stage cervical carcinoma and high-grade precancerous lesions, ROMO1 may be a useful auxiliary biomarker.